Charge Transport and Charge Recombination
Charge carrier transport and carrier recombination govern the operation of all electronic devices, including those utilizing organic semiconductors. Thus, understanding charge transport and charge recombination in organic semiconductors is a prerequisite for successfully designing future high performance organic electronic devices.
In our group, we study charge carrier transport by fabricating field-effect transistors and what are known as single carrier devices. Understanding the energetics of the organic materials allows us to isolate either hole or electron transport by choosing electrode materials with the correct work functions relative to the frontier energy levels of a given organic compound. Analysis of the current–voltage characteristics of these devices provides information about how fast these charge carriers are transported through the organic material and if the organic material under investigation possesses the right properties to be used in high performance organic solar cells, field-effect transistors, or light emitting diodes.
We employ a variety of techniques to understand the recombination mechanisms in organic semiconductors. Studying double carrier devices enables us to investigate the process of holes recombining with electrons. This process is a fundamental loss mechanism in organic solar cells, but is essential to the operation of light emitting diodes. Additionally, we probe recombination mechanisms by looking at the photoluminescence, electroluminescence, quantum efficiency, and impedance response of organic electronic devices as a function of temperature and excitation energy.